Grinding and polishing lathe



June 2, 1931. R. c. MITCHELL GRINDING AND POLISHING LATHE Filed May 9, 1924 2 Sheets-Sheet J.

June 2, 1931. R. c. MITCHELL GRINDING AND POLISHING LATHE Filed May 9, 1924 2 Sheets-Sheet 2 Patented June 2, 19 31 l",808,17'ZB ATES mmonn 1c. MITCHELL, or SPRINGFIELD, onto; ns'srenon .rozrnn ,nirennrt GINEEBING'CQ, or SPRINGFIELD, 01110, A eoRroRe'rIo 'ono-Iiro GRINDING AND Forearmame Application filed May 9, 1924. Serial no; 711,987.

My invention relates to grinding and pol ishing lathe's and more particularly to a-self contained unitary duplex lathe employing two spindles independently driven from a single motor.

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those lathes wherein It has been customary heretofore to drive the spindles of such polishing and buffing lat-hes and grinding machines from an overhead line shaft, or from a motor or other source of power outside the'lathe itself. In

the driving motor is embodied in the lathe as a single unit, "the usual construction has been to employ ghe' or armature shaft of the'gmotor'as asp indie mounting the grinder or buffing wheel... T he objection to suchcon'struction is that the constant motor speed is=not always the *mostzdesirable, nor most efficientspeedfor a buffing wheel, polishing wheels or grinder member. Moreover, in such construction wherein double spindles were employed to carrying different typesof polishing or buffing wheels, or a grinder and a bufiing wheel,

buffing "lathe, having two independently mounted revoluble'spindles, each separately driven -by lathe. This drivingimotor 1s provided with .a drivepulley at each end. :Instead of em ploying clutches or fastand loose pulleys,

the driving belts are madeunusually lon'gsothat normally they will hang loosely about the pulleys without driving contact, and belt tighteners are employed to take up the slackin the belt, when the spindlesare to be driven. The belt tighteners, for the respective belts belt maybe released or tightened independ ently of the other, stopped-for the interchange of driving or polishing wheels, without interfering with the operation of the otherspindle.

r The object of the invention is to simplify the structure,-as well as the means and mode of operation of grinding and polishing Lathes, whereby they will not only becheapit has been? necessary'to stop the motor in order to change elements upon either spindle.

"In the {present invention there is contemplated the unitary polishing, grinding orbelted connection with :a driving motor inclosed within the pedestal ofthecr ed in construction, sbllil will be moreiefii-i cientinsuse, positiveinoperation unifonmin '1 action and unlikelytogetont-iof repair.

1A further obj ect of the invention '15 to pro-- vide a self contained unitary :lathe, wherein ing the safety of operation,

'A furthenob'eclt ofithe i vention'is to provide a duplex lathe,or one havling two spin.

single motor, withoutthe necessity of belt shifting or-clutch ,m'echanism.

Aafu'rther obj ect of the invention .is itO provide practical means for interconnecting and disconnecting-the motor and the respective no 7 .dles, operable independently at will from, a

spindles by varying the tensionoftthe drive belt.

Afurther object iinvention isito provide an improved form of-belt tightener andto further provide atake up' means forvary ingthe relationiof the belt withthedriving pulley independent of the belt itightenern a With the above primary'and other incidental'objects in view as willmoreifully appear in the specification, the invention :con-

sists of the features of construction,tthe parts and -combinations ithereof,j=and-, the

modeof operation or their equivalents as hereinafter 'described 'andw-set :forth inrthe g}; 7

claims In the accompanying drawings, wherein Eis shown the preferred, but obviously not necess arily the only s-form :of :embodimentof the invention, Fig. '1 isa front -.elevation of the assembled duplex lathe forming the 'subj ect matter hereof, with a portion :of the housing or pedestal broken away; '2 is an end elevation thereof, alsoihaving the "housing broken away ztlo v disclose jithe' location and relation ,of the driving motor, and ibelt. con- Like parts areiindicated by similarscharac- .ters oft-reference :throughout itheseveral i l 1 i V e v 1 Due tothe'fixed and-unalterable speeds at which alternating current motors operate, it

is-notpossibleto obtain themost desirable or correct spindle or wheel speed for all polish: f

ing and buffing" oper'ations, 'awithiy; 0

'ening devices; bufiing wwheels is a frequentnecessity. The

present'construction enables the stopping of either spindle for interchange or replacement motor driven polishing lathes, wherein the grinding and polishing wheels, are mounted upon extensions of the armature shaft. By the present motor driven unit, wherein the motor is mounted in the base of the machine,

and belted to the wheel spindles, .any desired spindle or wheelspeed may be attained by varying the vproportions of the driven and driving pulleys, irrespective of the, speed of the motor. Moreover, this construction per-' mits the starting and stopping of either spindle of a duplex lathe, independent of the other spindle, by means of hand levers on opposite sides of the machine controlling the engagement and disengagement of belt tight- Change of polishing and of wheels, without the necessity of stopping the motor or interfering with the operation of other spindles. This is highly important and results in great decrease of production costs, particularly when two 0 erations are asslgned to thesame machine.

duplex construction enables different-opera therwise the v tions of grinding, buifin'gandpolishing to be performed upon the same machine Without the necessity o f'fre quentchange of wheels" which may be driven at different speeds.

While the lathe spindles may bejben ch 'mounted, or the mounting may be in -the form porting of a table or frame provided with legs, the

preferred construction isan enclosed hollow pedestal 1, havingat its top bearings for: independent but axially a-lined spindles'2 and 3. These spindles projectbeyond'thefsuppedestal 1, in opposite directions and are fitted and adapted'to carryingthe-necessary grinding wheelspolishing andbufling wheels or other elements to berotate'd. The

spindles 2 and 3 are mounted 'in ball bear ingcollars 4. The outer bearing upon which the greatest strain fails is"'preferably a double ball bearing, whilethe innermost. bearings of the respective spin-dles'may be The ball bearing collars 4 single bearings;

. .j are mounted in sleeves 5,and .6, having limit provided with external spherical zones which ed. degreefof universal or wobble adjustment. To this end the mounting sleeves 5 and 6 are seat'within correspondingly concaved bear ings'in heads or split collars 7 upon the main supporting pedestal or :frame. The interior surfaces of the heads 'or collars 7 may be machined OIOtllBIWlSG formed to conform close I lytojthe exterior contour of the mounting jsleeves'5 and 6. "An economical method offorming such concave bearings, without the necessity of machine operation is descri'bedin my .1 co -pending gapplicatijon'"Serial No. 2554,119, filed April 17,1922. *This method consists casting'in 'situwithfin the bearing v head'or' collar7 an interliner offmetal'byemiploying the mounting sleeve as a core about which the interliner is cast and to which it is made to accurately conform. It is obvious that other methods of mounting the sleeves 5 and. 6 for limited universal adjustment may beemployed. Such universal adjustment or Wobble movement of the sleeves 5 and 6 render the spindle bearings self alining. The

' spindle.

orly disposed upon loose driving within the hollow pedestal or frame of the machine. pulleys 10 on the opposite ends of its armature shaft. The driving pulleys 10 upon the" v armature shaft areinterconnected .with the driven I belts 1 These belts 11 are of abnormal lengtli,whereby when unsubj'ected to tension they will hang loosely from the driven pill-- This motor 9 isprovided with,

pulleys 8 upon the spindles by driving ley 8, around the driving pulley 10 but, out

of contact therewith. Thus due to the'exces sive slackin the belt 11, the motor will nor-.

mally' afford no driving effect. 'Pivotedat 12 in the main frame or pcjdestal is abelt" tightener arm l3 carrying an idler pulleyl l. The belt tightener through its pivotal shaft with a weight arm 15 carrying thereon'a Weight body 16,which operates by gravity to oscillate'the'i'dler l l against thebelt 11 to take up itsslack and insure driving contact with ley 10. .The weight 16 maybe adjusted upon the driving pul 1-3 is interconnected j the arm15 to'and from the pivotal connection thereof to" vary'the belt tightening pressure) Theshaft'12 ofthe belt'tightener projects beyond the pedestal 1 and carries exteriorly 7 thereof a hand lever 17, by which the weight.

16 and with it theidler pulley'lfl may be os- Cmat'ed upwardly and e w rdly to relieve 1 the tension pressure upon the belt and so release the belt from driving Contact with the motor pulley 10. A pivoted latch 18'exterithe pedestal 1 serves to hold the hand lever and the belt tightener pulley 14 and weight 16 in inoperative position.

10 due to the excessive slack. Bydisengaging the hand-lever from the detentpawl 18,

the idler pulleyj 1 1 tensions the beltv under the influence of the Weight 16 with sufiicient pressure to aflord thenecessary driving'en gagement between ther'belt anddriving pu'lley. This pressurefcan be regulated by-ad- 5T5 justing the weight 16 -up'o n thearm 15, to en- 17 in retracted position" At such time; the 1 drive belt 11 hangs loosely about the pulley able the beltto slip when undue resistance to r rotation of the" spindle is encountered." Thus the tensioning and release of the-excessively belt'by means of the blt tightsafety provision for the adjustment of the driving tension by variation of the weight 16 to cause the belt to slip when subjected to any undue driving resistance. 1

As a means of taking up undue slack in the belt independent of the belt tightener or compensate for stretching the motor 9 is mounted upon a base 19, hinged at 20, the opposite edge within the limits of the slot 21. The base may be clamped in any position of adjustment by the clamp bolts 22, j

From the above description it will be apparent that there is thus provided a device of the character described possessing theparticular features of advantage before enumer- 2 ated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advan- 2 tages.

While in order to comply with the statute the invention has been describedin language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific details shown, but that the means and construction herein disclosed comprises the preferred form of several modes of putting the invention into effectand the invention is, therefore, claimed in any of 5 its forms or modifications within the legitimate and valid scope of the appended claims; Having thus described my invention, I claim:

1. In a construction of the character de- -0 scribed a hollow supporting pedestal, a shelf mounted in the lower portion of said pedestal for oscillatory movement in a vertical direction, means for in different positions of swinging adjustment, a motor mounted upon saidshelf within the hollow pedestal, of said pedestal, drive anddriven pulleys carried by the motor and spindle respectively, a

belt having therein excessive slack connecto ing said driving and driven pulleys, automatic belt tightener means for taking up the slack of said belt, an operating lever located exteriorly of the pedestal and connected with the belt tightener means for retractent driving belts of excessive length connecting the respective spindles and driving means,

of which is adjustable vertically means operable securing said oscillatory shelftiv s i dl s,

a spindle located'at the top ing said belt tightener and relaxing the driving tension of the belt and a detent extending and normally lacking driving contact there-' ening means for tensionmg'either of the belts independent of the other into driving engagement, detent means for temporarily holding the belt tightening means in inoperative condition, and means for adjusting the tension of said belts in unison independent of the aforementioned independent belt tightening means.

3. In a grinding and polishinglathe'or the like, a supporting pedestal, a pair of independently revoluble spindles mounted thereon, driving means therefor, drive belts of excessive length connecting the drive means and respective spindles, and lacking driving conwith, automatically adjustable belt tighttact therewith when relaxed, an adjustable V mounting for said means by variation of which the tension of the drive belts may be adjusted in unison, and independently operable belt tightening devices by which the tension of the respective belts may be inde pendently varied additionally to such unison adjustment.

4:. In a grinding and polishing lathe or the like, a supporting pedestal, a pair of independently revoluble spindles mounted thereon, a driving motormounted within the ped estal, drive belts of excessive length connectingthe drive motor and respective spindles, and lacking driving contact therewith when relaxed, independent gravity operated belt tightener means for the respective belts,

estal for retracting the belt tightener means,

from the exterior of the ped- "are and detents for temporarily holding the belt tightener means in inoperative positions.

5. In a grinding and polishing lathe, a

supporting pedestal,independently revoluble spindles carried thereby, a single motor common to both spindles, independent drive belts 1 ofexcessive length connecting the-motor and which, when relaxed, lack driving contact therewith, an adjustable mounting for the motor whereby the tension of said belts may be adjusted simultaneously I by the motor adjustment and independently operable belt tighteners one for each belt by r which the belt tension maybe adjusted independent of the motor adjustment and also independent of each other.

I have hereunto set my hand this 30 day of April A. D. 1924. l

' RAYMOND, o. MITCHELL.

In testimony whereof, 

